Telephone-exchange system



June 19, 1923. 1,459,175

F. ALDENDORFF TELEPHONE EXCHANGE SYSTEM Filed'Dec. 31, 1914 11 sheets-sheet 1 June 19, 39523.

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F. ALDENDQRFF TELEPHONE EXCHANGE SYSTEM Filed Dec. 51, 1914.-

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F. ALDENDORFF TELEPHONE EXCHqXNGE SYSTEM Filed Dec. 51, 1914 11 sheets-sheet 7 June 19, E923. 3 459 3 55 F.ALDENDORFF TELEPHONE EXCHANGE SYSTEM Filed Dec. 51, 1914 11 sheet$-sheet a June 19, wzs. 1,459,175

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F. ALDENDORFF TELEPHONE EXCHANGE SYSTEM Filed Dec. 51,1914 11 sheets-sheet l1 Patented June 19, 1923.

once.

TELEPHONE-EXCHANGE SYSTEM.

Application filed December 31, 1914.

Serial No. 879,950.

(GRANTED UNDER THE PROVISIONS OF THE ACT OFT/[ARCH 3, 1921, 41 STAT.'L., 1313.)

To all whom it may, concern:

one end of a link circuit containing an operators switch controller being automatically connected to a. free slow-acting finder and to a free selector associated therewith whenever the switch controller by its con trolling currents has caused a switch or set of switches to establish a connection with a wanted line, whilst the other end of the said link circuit is automatically connected to a subscribers line as soon as the subscriber calls.

Each connection between two subscribers is first established through a relatively quick-acting switch or finder. The quick- .of the calling subscriber.

acting finder is in one link circuit extending between calling line'and a selector, and

the slow-acting finder is in another link circuit between the said line and selector. The

'momenta connection through the link circuit containing the quick-actingfinder"has been established between two subscribers this link circuit is disconnected from the established connection and connected to another idle selector.

The quick-acting finders are each provided with several simultaneously-operating test brushes the number of which is greater than that of the testbrushes on the slowact-ing finders. hena subscriber calls the next idle quick-acting finder in the group of switches: to which he belongs is started by a current impulse produced by the line relay This current im pulse flows through a contact of the cut-off relay of the calling subscriber. When the cut-off relay is energized the :said starting impulse circuit is opened and the flowing of a wrong starting impulse on the deenergization of the line relay is thus prevented.

The operators switch controllers in the new system each consist of two impulse counting brushes. Associated with each brush is a relay the operation of which is madedependent on the testing and change over functions of the selectors controlled by the switch controller. The moment one of these relays is causedto operate as a result of a testing or change over function, it starts the operation of the next impulse counting brush that is due act. The said relays are switched into the controlling circuit extending from the operators controller to the selectors before the testing or change over functions in these selectors take place. The moment one of these functions is per formed the part ofthe controlling circuit extending from the selector to the controller is momentarilyopened by a. device. in the selector. By this means the relay in the controlling circuit at the controller-is momentarilydeenergized and this momentary decnergization of the relay results in the operation of the impulse counting brush inv the controller being started that counts the impulses in the next series of. selector controlling impulses.

Another feature of the invention consists in a novel arrangement of the starting circuit of the operators finders. Usually this starting circuit is extended in a known manner to the next idle finder the moment a finder is taken into use. The new feature consists in the starting circuit which leads to the quick-acting finder of a certainoperator being extended, when this operator connects herself to a calling line, straight to the finders of another operator.

An advantage obtained by usingquickacting finders with several test brushes in the operators link circuits and relatively slow- ..acting finders in link circuits through WlllCh replaced by a linkcircuit with a slower" actin g finder having fewer test brushes, may be used with equal advantage both in full auto matic and semi-automatic exchanges.

Another feature of this invention is directed to the means for causing a secondary link circuit, to which a primary link clrcuit that takes up a call is connected, to be connected without fail by its connecting switch to no other line but the particular calling line to Which the said primary link circuit has been connected. It is clear, that .infa practical exchange several calls w l originate at times in various groups simultaneously and in each group several calls i may be sent in at practically the same motook a call and also the line in that group tain ed.

link switches, that connect the secondary link cirment. An identifying means is provided which enables a secondary llnk circuit to identify the group of lines from which it from. which the call proceeded. If no such means were provided, wrong connections would be obtained by calling subscribers, for the'call sent in by a subscriber and passed on by. a primary link circuit to a certain sec ondary link circuit represents a certain wanted number, and if the secondary link circuit were to be connected to a second calling subscriber, the result would be that the second calling subscriber would be con nected through group and final selectors to the called line that is wantedby the first subscriber.

The identifying means consist in a special identifying circuit for each primary link circuit being provided in the secondary link circuits or in the switches ljielonging to the secondary link circuits through which the established talking connections are main- Another feature of the invention consists in an arrangement of the secondary circuits by which. the connection cuits directly to the subscribers lines, may be used both for incoming calls and for outgoing calls .or in other words for extending a calling subscribers line to a group selecitor and at other times for extending a connection from a group selector to a wanted 'pa nying drawing.

subscribers line.

The invention will now be explained by the aid of the accompanying drawings.

The invention is illustrated in the accomm A complete diagram is obtained by placing Figs. 1, 2, l and 5 bes de each other. Fig. 1 shows the subscrlbers lines with their relays, the brushes link circuit.

of the quick-acting finders and of the slowacting finders, and the multiple connections of the subscribers to the bank contacts of the said finders. Fig. 2 illustrates the relays and ele'ctro-magnets of the slow-acting and quick-acting finders and the keyboard of an operators switch controller. In Fig. 3 the other devices belonging to the switch controller are shown. Fig. 4 represents a trunk finder and Fig. 5 a group selector.

Fig. 6 shows a method ofapplying the invention in, which the primary link circuits of each comprising an operators keyboard BS. are connected to the lines of calling subscribers by two finders HS. and S in tandem whenever a subscriber calls. The finder I-LS. by its operation in connecting to a calling line in a certain group causes its associated selector finder VS. to pick out the group from which the call was received and to connect to a free secondary link circuit Lin that group. selector G and the slow acting finder V belonging to the free secondary link circuit may then be operated simultaneously the group selector extending the connection from the secondary link circuit towards the wanted subscriber and the slow acting finder extending the connection from the link circuit towards the calling subscriber.

Fig. 7 illustrates a modification of the selector finders VS of Fig. 6.

Figs. 8 and 8 when placed side by side show another way of applying the invention. Here the primary link circuits each extending between a switch 72,8 and a switch VS are always immediately connected by their selector finders VS V55 to a free secondary link circuit 72] the moment they are disconnected from an engaged secondary The primary link circuits are connected to calling lines by means of two switches [L8 and s, and the secondary link circuits are also connected to the calling lines bytwo switches in; and V in tandem.

When a call comes-through from any par- The group ticular group e. g. group I to a primary link circuit this primary link circuit will already be connected by its selector finder e. g.-VS to a free secondary link circuit e. g. M and the auxiliary slow. finder 7W will be immediately started. It will first select the group I from whence the call came and will then pick out a free multiple wire e. Z leading to an idle slow-acting finder V This finder will then be caused to select the calling line. During the time in which the connection is being extended from the seized secondary link circuit M to or towards the calling subscriber it will also be extended through the group selector 9 and through the further selectors to or towards the wanted subscriber.

This method of extending a connection from a middle point through a number of selectors-towards both the calling and called subscriber also forms a feature of this invention.

Fig. 9 shows a method by which the number of brushes required on the selector finders VS can be diminished in number.

Fig. 10 shows how the auxiliary slow finders 72/0 and the group selectors g or an exchange may both be connected to the multiples leading to the slow acting finders Y. In a case like this the slow acting finders are provided with means which cause them to act as final selectors whenever a call is extended to them through a group selector 5/.

Fig. 11 illustrates an application of the switching method shown in Fig. 10' to an exchange in which there are minor groups each consisting of a plurality or" small groups 1, 2 and. major groups each comprising" a plurality of minor. groups; This indicates how the principle consisting in extending a connection from a middle point through a number of selectors towards both the calling and called subscribers disclosed in Figs. 5 t0 9 may be applied. to systems of any size. I

In Fig. 1, S S indicate two subscribers stations whilst TF LR and TR LR are the cut-off and line relays belonging to these stations. Station S2 for, example is connected by lines A2, B2, C2 to sets of bank contacts int-he slow-acting and quickacting finders. All the other subscribers in the same group are connected in a simi lar manner to corresponding sets of bank contacts in the quick-acting and slow-acting finders.

The slow-acting finders each have a setof brushes "m, 12?), we, ml, "06 that is moved by means of a motor magnet Me over sets of fixed bank contacts. The quick-acting finders F are each provided with several sets of brushes, e. g. 10, all of which are moved together over sets of bank contacts by a motor magnet Mr. By means of its several sets of brushes each quick-acting finder hunts in, several sub-groups of sub scribers lines simultaneously for a calling line, so that ii"? ten setsof brushes such as, a1, bl, cl, (Z1 and a2. b2, 02, (Z2 are used, the quick-acting finder needs only to. travel the distance covered by ten contact sets .in order to pick a calling line out of a hundred lines. Each brush set 41, b1, 01, all or a2, 62. c2. (Z2 has a test relay 391 or 792, which is energized when its set ofbrushes reaches a calling line and then connects the calling line to alink circuit or operators position. A calling lamp AL is then lighted on the operators position whereupon the operator answers the call. Having obtained the number of the desired line the operator writes down this number on the keyboard by depressinga thousands, hundreds, tens and units key. The switch controller thereupon commences sending selecting impulses to the selectors in the'exchange "and these selectors establish a connection" with the wanted subscriber. is made a second connection is established over another path comprising a slow-acting finder, which meanwhile has hunted and found the calling line, and the first connection comprising the quick-acting finder F and the trunk finder Fig. at is disrupted, and the trunk finder immediatelyconne cts the quick-acting finder to another idle selector Fig. 5.

The operation of all the circuits will now be described in detail. I 7

When a subscriber e. S2 makes a call a current flows from the negative pole of the exchange battery through LE2, 1, 81. S2, .92, 2, to earth. The line relay LE2 is thus energized and closes its contact 3 which connects earth to the test wire C2 of the calling line by way of 3. 8, TR2. Electrical calling potential is thus applied to the test contacts in the quick-actingand slow-acting finders.

The line relay LE2 operates'on its energiza-tion the contact springs 4,5, 6. The spring a is pressed against spring5 and this spring is then moved away from spring 6.

By this means a current impulse is sent-from, .95

earth through 7, 4L, 5, 6, starting wire .31. contact 10, of an off-normal switch 0S of WVhen this connectionthe nextidle quick-acting finder. F in the group, motor magnet Ma, contacts, 11, 12 of the test relavs of the quick-acting finder to the negative pole. As soon as the springo leavesthe spring 6this impulse through'the motor magnet Mr ceases and the armature of the motor magnet in falling back then moves the. brush sets or the quick-acting finder out of their normal position. The moment the brush sets of the quick-acting finder are moved out of their normal position the off-normal switch OS is shitted and its contacts 13, 14;, '15 are closed whilst its contact 10 is opened. By the opening or contact 10 and the simultaneous closure or contactlst the starting wire sZ 1s d1sconnectedirom the quickeacting finder F and ex-.

tended to the next quiclcacting finder- F1 belonging to the next link circuit. Bythe closure of contact 13 an interrupter 16 is connected to the motor magnet -Mr and impulses then fiow from the earthfthrough 16, 13. Mr, contacts 11, 12 the negative pole and these impulses cause'the magnet Mr to move the brush sets or the quick-acting finder over the bank contacts connected to the subscribers lines. The moment a set of brushes e; a1, 61, cl, (Z1 reaches a set of bank contacts e. 79c, 79?), p0, pd, that belongs to a calling line, a current fiows from the negative pole or the battery through 1?,contacts 1 19 of the various test relays. common battery lead 530 to the 'zrmtart 2i oi the test relay whose brush 01 has reached the-calling line, Winding of test relay. pl, 01, 190, C2, cut-ofit relay T132 contact 8, 3 to the earth. The cut-ofi' relay T112 is energized and closes through a contact 9 a locking circuit "for itself that is independent of the contact 3. At the same. timethe cut-oft relay disconnects the line relay from the calling lineby opening the contacts 1. and In order to prevent the momentary connection between the contact springs 4t, 5, and 6, which takes place when the armature ot the line relay drops back, from causing another impulse to be sent through thestartingwire $7 and thereby starting another quick-acting finder F1, the connection between the contact spring 1 and earth is broken at contact when the cut-off relay is energized.

The test relay pl that is energized in the quiclnacting finder in the manner described above disconnects itself from the common battery lead leadingsto all the test relays p in that finder and switches itself at into an independent circuit. By opening its contact 18 the test relay QQZ cuts ottthe battery feed to all the other test relays on the same finder. By closingits contact 23 it short circuits a part of its winding and thus lowers the potential of the calling; line causing it to appear engaged. By closing its contact 25 it prepares a circuit which, soon after-- wards causes aslow-acting finder LV to set its brushesonto the particular calling line A2, B2, C2 that the quick-acting finder F has sought out; Finally the test relay p3 closes by its contact 26 thecircuit of a calling lamp AL and through its contacts 19 and 24L it extends the calling line s1, $2 to the position of an operator. The operator observing the lighting of the calling lamp AL depresses her listening key 27 and thus connects her talking apparatus TS to the calling line. After ascertaining the number oi I the wanted line, which will be assumed to be No. 4567, she depresses the keys T T T T and these keys are held in their depressed positions in a known manner by locking bars (not shown). A separatelocking bar is provided for each row of keys and each locking bar controls a contact that is individual to the particular row of keys. Thus the locking bar of the row oli thousands keys controls a contact 28. the locking bars ot' the hundreds, tens and units rows control contacts 29, 30 and Sliespectivelyl The locking bar of the units row controls an ad ditional contact 32; When a key in each row is depressed the contacts 28, 29, 30 and 31 are closed and thereby a relay 33 is energized by a current that flows from earth through a resist'ance3t, relay 33, 28, 29, 30, 31 to the negative pole. The relay 33 closes a locking circuit for itself through its contact 37, which circuit is independent ot the contacts 28, 29, 30 and 31. By opening its contacts 35, 36 it disconnects the calling line from the link circuit A3, B3 leading to the selectors and by closing a contact 38 it completes the circuit of a motor magnet 39 which moves an impulse counting brush l0 over a set of contacts tl-tlO. Each of these contacts are connected to keys in the thousands row T, and tens row T2.

located in a group selector Fig. 5.. This circuit may be traced from earth through the upper winding of the relay LC, side switch 15, contact 4:6 of a relay 47 line A l, brush B1 of the trunk finder, line A3, 4-3, 4:9, 50, 51, 4:3,el l, B3, B2, A5 side switch as, lower wind-- ing of the relay LC to the other pole of the battery. Each attraction of the armature 52 results in this controlling circuit being opened and in the controlling relay LC clos-- ing its contacts 53 and 54.

Beiore tracing any further the course of the connection through the group selectors and the final selector, the events will now be described that take place (simultaneously with the events in the quick-acting finder) in the slow-acting finder LVl that is associated. with the group selector Fig. 5.

The starting impulse that is sent when a subscriber calls through the starting wire sZ flows not only through the motor magnet Mr as already described but also through the wire 58, contact 59, wire 60. contact 61,.brush 134-, wire 62, motor magnet Me; of the slow acting finder LVl to earth.

When this startingimpulse through the motor magnet M1" ceases the of? normal switch OS is shifted as previously described 'The moment the set of bank contacts is reached, which corresponds to the set oi contacts upon which the brush set of the quickacting finder F is resting, a current flows from the negative pole through the wire 65, contact of the test relay pl, brush (ZZ, contact 79d, wireD2, contact do, brush ml, stopping wire lull, brush B7 of the trunk finder Fig. l, stopping relay H to the positive pole of the battery. Thestopping relay H opens the contact 61 and thus stops the operation of the motor magnet Mo so that the brush set of the slow acting finder stops on the set of bank contact which belongs to the calling line. A. talking connection is not, however, established through the brushes of the slowacting finder until the connecting relay DR is energized and this energization only takes place after all the group selectors and the final selector used for the connection'have completed their operations.

The events in the establishing of a connection through the selectors under the in liuence of a switch controller have been described up to the point where the circuit of the magnet 39 was closed and the operation of the impulse counting brush 40 commenced. At each step that the counting brush 40 is caused to take the contact 43 is opened and the controlling circuit containing the controlling relay LC or" the group selector interrupted. At each interruption the controlling relay LC closes a contact 53 and causes a selecting impulse to flow from the negative pole through the contact 300 of a relay 63. 53, 70, vertical magnet HM of the selector which for example may be assumed to be of the Strowger type.

It is to be observed that the relay 63, was energized by the starting impulse that flowed through the brush B4 and the wire 62 and a portion of which went through 64, 301, 63 to earth, causing the relay 63 to switch itself into an independent locking circuit which includes the contacts 302 and 209.

The release relay RR is energized as soon as the controlling relay LC is energized in the manner described above. he current through the release relay flows from the T4, magnet Mt, contact arm 76, magnet Mo to the negative pole of the battery. When this impulse ceases the magnet Mt releases the locking bar of the row of thousands keys and the magnet M0 shifts the contact arm 76 to its next contact 117. opens the circuit of the motor magnet 39 at contact 41 so that the interruptions ot' the contact 43 and the impulses caused thereby in the controlling circuit A3, B3 cease. the same time the relay "(5 closes a contact 47 and opens the contact 51. This results in a relay 80 being included in the controlling circuit. The current through this relay flows from the earth. through LC, 45, A4, B1, A3, 48, 49, 50, 80, 47, 43, 44, B3, B2, A5, 46, LC back to the battery. The relay LC now keeps its armature attracted long enough to cause the change over relay CR,

The relay 75.

be traced from the earththrough S, 83, 81,

S2, 300 to the negative battery pole. The side switch magnet thereupon shifts the side switches 45,46, s4, s5, .86, 87, 88, 89,207 into their second positions which results in the closure of the circuit of the rotary magnet DM of the group selector bythe side switch 85. This circuit extends from the negative pole of the battery through the impulser 90, contact 91, of the test relay PR, DM to earth. The rotary magnet now turns the brushes a, go, go causing them to brush over the sets of bank contacts (that are each connected to a trunk A6, B6, C6) until a trunk leading to an idle second selector in the wanted thousand ground is found. The moment the test brush 0 reaches the test contact of an idle trunk a current flows from the negative battery pole through the test relay PR, 89, 0, to test wire C6 and through a contact 93 and a resistance 92 in an idle second group selector. The test relay PR is energized and opens the circuit of the rotary magnet at its contacts 91. At its con tact 94 the test relay short circuits a part of its winding thus lowering the potential on the test wire C6 and making the trunk A6, B6, C6 appear engaged. The test relay also causes the contact spring 95 to be pressed against a contact spring 96 which latter is thus moved away from another contact 97. By this action of the springs 95, 96, 97 and similar springs 95 96 97 wires 98 and 98 are momentarily connected to the negative pole of the battery and this results in current impulses being sent simultaneously through the sideswitch magnet S and a relay 47. The side switch magnet movesthe contact arms of the side switch into their third positions which results in the circuit A4, A5 being extended through 87, 88 to the neXt selector and the controlling relay LC being disconnected from the leads to the operators controller. The wires A4, A5 are extended to the next group'sele'c tor by the switches 87, 88 before the controlling relay LC of the group selector. Fig. 5 is discone nected. so that the no interruption'of the controlling circuit or of the current flowing through the relay takes place when the controlling circuit is extended. But the relay 47 short circuits the controlling circuit by its contact 99 and opens by its contact 46 the current path extending through A4, B1, 48, 49, 50, 80, 47, 43, 44, B3, B2, A4 which results in the deenergization ot the relay 80 of the controller. The armature 100 of this relay in travelling back momentarily closes a contact 101 by which the restoring magnet 103 of the counting brush 40 and also a relay 102 is energized. The restoring magnet ,103 closes its armature contact 104 and thus switches itself into a locking circuit which extends from the negative pole through the contact 105, 104, 103 to earth. The contact 105 is an off-normal contact that is closed as soon as the counting brush 40 is moved out of its normal position. The moment the counting brush after being released by the magnet 103, reaches its normal position, the contact 105 is opened and the locking circuit of the magnet 103 is broken.

When the relay 102 is energized as described it closes a locking circuit for itself through the contacts 106 and 107 and it also closes a shunt about the contacts 43 and 51 by its contact 108. At the same time it closes by its contact 109 the circuit of themotor magnet 01' the counting brush 140. In this circuit currentimpulses flow from the earth through the impulser 122, 111, 109, 110 to the negative battery pole. At each impulse the magnet 110 moves the counting brush 140 onto another contact in the contact set h1-h10.

The relay 47 in the group selector Fig. 5 will meanwhile have allowed its amature to drop back so as to reestablish the controlling circuit by its contact 46. Therefore the interruptions of the contact 50, the number of which corresponds to the number of steps of the counting brush 140, will act upon the controlling relay in the second group selector similarly as they influenced the controlling relay LC of the group selector Fig. 5. As soon as the counting brush 140 has been advanced to the contact 7L5, that is connected to the depressed hundreds key T5, a current flows from the earth through the resistance 113, relay 114, 115, 140, 7L5, T5, magnet Mk, contact 117, contact arm 76. magnet M0, to the negative pole. The relay 114 is then energized and switches itself into a locking circuit through closing its contact 120. At the same time it opens the circuit of the magnet 110 at its contact 111 and closes the circuit of the restoring magnet 122 at its contact 121. The restoring magnet is thus energized and restores the counting brush 140 to its normal position. Whilst the counting brush is travelling back to its normal position the restoring magnet is kept energized by a locking circuit which includes the contacts 123, 124 and which is opened at the contact 124 when the counting brush 140 regains its normal position.

The relay 114 also closes the contact 126 and opens a contact 49 and thereby introduces a relay 125 into the selector controlling circuit. The relay 125 is then immediately energized by a current flowing from the second group selector and through the controlling loop similarly as the relay 80 was energized by a current flowing through the controlling relay LC of the first group selector Fig. 5 and through the controlling circuit.

By the interruptions of the contact 50 the second group selector will now have been raised to the level of bank contacts that leads to the final selectors in the wanted hundred group. During the interval of steady closure of the contact 50 which ensues after the transmission of the selecting impulses the second group selector is caused to change over in a known manner from the selecting to the trunk hunting function. The moment a free trunk is found a relay in the second group selector, which is similar to the relay 47, Fig. 5 opens the portion of the controlling circuit that extends to the operators switch controller so that the relay 125 in the controller is deenergized. The armature of this relay then falls back and in so doing momentarily closes the contacts 128, 129, which short circuits the relays 75 and 114 and thus deenergized them. The relay 75 then closes the contact 41 and thus causes a renewed operation of the counting brush 40 by the motor magnet 39. It also opens the circuit of the relay 102.

The counting brush 40.is now stepped forward a second time and the third series of impulses is sent over the controlling circuit by the interruption of the contact 43. The motion f the counting brush 40 and the interruptions of 43 continue until the counting brush reaches a contact 66 that is connected to the depressed tens key T6 when a current flows from the earth through 74, 75, 40, 256, T6, M2, 118, 76 to'the negative battery pole. The relay 75 then deenergizes the magnet 39 and introduces the relay 80 into the controlling circuit in the manner already described. The controlling circuit is then kept steadily closed and this causes the change over to take place in the final selector from the vertical to the horizontal rotary movement. The final selectors are arranged so that at the moment the change over takes place a relay similar to 47', Fig. 5 is momentarily energized so as to cause a brief opening of the part of the controlling circuit that extends backto the operators controller. By this opening of the controlling circuit the armature is caused to fall back so as to momentarily close a contact 101. and this results in the counting brush 40 being restoredby the restoring magnet 103 and in the energization of the relay 102 in the manner already described. The relay 102 remains energized until-the relay 75, is deprived of its locking current bv the resistance 74 being shortrcircuited, the Said locking current fiowing through the contact 130. The energization of the'relay 102 result in the closure of the circuit of the motor magnet 110. The motor magnet then receives impulses from the impulser 112 and moves the counting brush 140 over the con tacts h1h10 a second time. At each step taken by the counting brush 1 10 the controlling circuit is interrupted at contact 50- and at each interruption the brushes of the final selector are rotated one step in a known manner. When the counting brush 140 reaches the contact it? that is connected to the depressed units key T7 a current flows from earth through 113, 1141, 115, 1 10, 7L7, T7. Me, 119, Mo to the negative battery pole. The relay 11 1 opens the circuit of the motor magnet 1.10 and closes the circuit of the restoring magnet by itscontact .121 thus causing the counting brush 1410 to be restored to its normal position. The current impulse that flows through the counting brush 1&0 and through T7, Me, Me, causes the contact arm 76 to be shifted from the contact 119 to 116 so that this arm will now have regained its normal position. In the movement of the contact arm 76 from the contact 116 to the contacts 117, 118, 119, and back to 11.6 the magnets Mt, Mh, Me, Me each received a current impulse and each of these magnets shifted a separate locking bar (not shown) and thereby released the depressed key in its row in a well known manner. It also restored the special contacts such as 28 associated with its row of keys. Therefore when all the depressed keys T4, T5, T6, T7 are released the special contacts 28, 29, 30, 31 will all be opened and the contact 32, closed. By the closure of the contact 32 of the row of units keys the circuit for stopping theoperation of the operators switch controller is prepared. The stoppage of the controller is caused by the opening of contact 38 i. e. by the deenergization of the relay and this relay is deenergized when the contact 32 is closed and the relay 125 allows its armature 127 to fallback.

l/Vhen the relay 114 is energized (after the units impulses that cause the rotary movement of the final selector have been sent) and the counting arm 1A0 is restored and the contact 32 closed, it closes the contact 126 whilst opening the contact 49. By this means the relay 11 1 introduces the relay 125 into the controlling circuit that extends from the final selector. After the final selector has been moved by the units impulses produced by the contact 50 onto the desired cuhscribefs line and the operation of contact 50 has been caused to cease by the energization of the relay 114: the controlling circuit extending from the final selector is closed to an appreciable length of time through the relay 125 in the same way as this took place after the peration of the second group selector. After a certain interval the final selector then changes over in a known manner from the units selecting function to testing the wanted line and in so doing causes a relay which is similar to relay 47, Fig. 5 to open the part of the controlling circuit that extends to the switch controller. This results in the deenergization of the relay 125 and in the detraction of the armature 127 which in falling back momentarily closes the contacts 127, 128 and deenergizes the relays 1141, and 33 by short-circuiting them. Of course these relays might just as well be deenergized by the armature 127 opening their circuits instead of short circuiting them. The deenergization of relay 33 results in the opening of the circuit of the magnet 39 so that a renewed operation of this magnet and of the contact 13 will not take place when the armature contact 41-1 is closed by the decnergization of the relay 7 5. When the armature of the relay 75 falls back the locking circuitof the relay 102 is opened at 107 so that after the final detraction of the armature 127 all the parts of the operator controller will be in their normal position.

When the armature of the relay 3% falls back the contact 180'is momentarily closed and the relays 181 and DR, Fig. 2 are thus cnergized. The former causes the quick-acting finder to be restored to its normal position and the latter connects the calling subscriher to the called subscriber through the brushes of the slow-acting finder and through the group selectors and final selector.

The circuit of the relay 181 may be traced from the negative pole through 180. 183, 181 to the positive pole. This relay opens at its contact 17 the battery lead to the test relays 791, 222, etc., and thus prevent a test relay from being energized during the restoration of the finder it a test brush (7 should. strike upon the earthed contact of a calling line. By its contact 186 the relay 181 closes the circuit of the motor magnet Mr (earth, 16, 13, Mr, 186, negative pole) and by its contact 182 it closes a locking circuit for itself which remains closed 'until the motor magnet Mr has moved the finder back into its normal position and has thus shifted the oil-normal switch so as to open the contact 15 and break the circuits of the relay 181 and of the magnet Mr.

The current that energized the relay DR flows from thenegative pole through 180,. 18 1-, B6, 185. 187. DR to earth. The relay DR closes a locking circuit through its contact 189 (earth, DR. 1.89, 191, 86, or 192. I

tained until the relay DH is deenergized at the end of the connection between the cal ing and called subscriber.

The relay DB in addition to connecting the calling subscribers line to the called line through its contacts 194-, 195 also produces a starting impulse for the trunk finder Fig. 4:. This starting impulse flows from the negative pole through 190 196, B8, starting relay 197 to earth. The relay 197 closes its contact 198 and thus completes a new circuit through B5. 199, 86 to the negative pole. By its contact 200 it closes the circuit of the motor magnet 201 which circuit extends "from earth through 200. 201, impulser 203 to the negative pole. The motor magnet now moves the brushes B1. B2, B4, B5, B6, B7, B8 of the trunk finder over sets of bank contacts leading to slow-acting finders and group selectorsuntil an idle selector is found. The wire 199 of each busy selector will be connected to the negative pole either through a contact 86 or 192 or through the contact'198 of another trunk finder Fig. 4 that is already connected to the particular trunk; As long as the brush B5 encounters wires 199 thus connected to the negative pole, the relay 197 is kept energized and the circuit of the motor magnet 201 remains closed at contact 200 so that the rotation of the brushes ot the trunk finder will continue until the test brush B5 strikes upon an idle test wire 199 i. e. a test wire that is not connected to the negative battery pole. As soon as this happens the relay 197 lets its armature 200 drop back opens the circuit of the motor magnet 201 and at the same time connects the negative pole to a wire 199 through its contact 198 The one end of the link circuit A3, B3 containii'ig the operators switch controller will then be connected to a new free trunk and the other end of this link circuit will be ready to be connected to another calling line by its quick-acting finder F. a

At the finish of the talking connection the slow-acting finder L1 1, the group selectors and the final selectors are released in any suitable known manner and a contact at 98, Fig. 5 will then be opened. This results in the deenergization of the test relay PR and in the closure of the contact 205. The release magnet RM of the first group selector will then be energized (earth 205, 206, 208, RM, negative pole) which causes the group selector to be released and the locking circuit of the relay 63 to be opened. By the release of the selector the side switch is moved back into its normal position and the negative battery pole will be disconnected by the switch arm 86 from the wire 191 so that the-connecting relay DR and the cut-off relay T132 of the calling line will be deenergized. The slow acting finder LV1 has no normal position and its brushes remain where the stand at the end of a connection until the inder is used in a fresh call.

In case a subscriber calls and only talks to the operator without having a connection setup through the selectors, the quick-acting finder used for the call is restored by a relay 230, Fig. 3 which is energized by a current that fiows to the calling subscriber as soon as the quick-acting finder makes the connection. When the subscriber replaces his receiver in a case like this. the falling back or"? the armature of relay 230 causes the momentary closure of a contact 2-31 and thus momentarily connects the negative pole to the wire-183. This energizes the relay 181 and this relay then causes the quick-acting finder F to be restored in the n'ianner previously described.

In order to prevent an operator from re ceiving more calls than she is able to handle expeditiously through several of her quick-.

acting finders being set onto calling lines a relay 2 10 is included in her talking circuit which is energized whenever she depresses her listening key 27 The relay 2 10 then causes the starting wire .92 to be connected directly to an extension wire 81] that leads straight to-the quick-acting finders oi the next operators position 0P2. This function may be performed by the relay 240 itself or by the aid of another relay 241.

An advantage obtained by using quickacting finders to connect the calling subscribers to the operators positions is that relatively large groups of subscribers may be formed and in spite of this the calls of subscribers will still be quickly passed on to idle operators. It is well known that by forming large groups of subscribers better trunking etficiency is obtained. If groups of two hundred subscribers are formed fifteen to seventeen slow-acting finders per group and three or fourv quickacting finderswith their switch controllers and trunk finders would generally give good service.

Although the slow-acting finders shown in the drawing have only one hunting brush no it is evident that several simultaneously hunting brushes c0 and brush sets ba, ob, nd, 416 may be provided. But it will generally be preferable to have more sets of brushes on the finders F than on the finders LV.

In Fig. 6 two groups (I and II) of subscribers T T T and T T T are shown. The lines of the subscribers that extend from their stations T to the exchange are connected in multiple to the fixed con tacts of all the quick-acting finders S and all the slow-acting finders V of the particular group. The line of subscriber T for example is thus multiply connected by taps or branches from the wire A In addition to the wire or wires connected to the line extending to each subscribers station local wires 6 6 l by the auxiliary quick-finder HS wires are provided at the exchange for each subscribers line, each of these local wires being connected in multiple to fixed contacts of the slow-acting finders V of the particular group, but being connected to only one of the quick-acting finders S of that group For example the subscriber T has two local The wire 6 is connected to a fixed contact in the middle contact row of each slow-acting finder V. The wire e is connected to a fixed contact in the left'hand contact row 'of each slow-acting finder V. But the wire 6 isconnected only to one quickacting finder S and the wire e only to the quick-acting finder S These wires form a part of the identifying means bywhich the slow-acting finders are enabled to identify the line from which the call proceeded that set them in action. The slow-acting finders each have one identifying brush for each set of identifying wires. There is an identifying brush 66 for the wlres connected to the quick-acting finder S and another brush 679 for the wires connected to the quick-acting finder S The quick-acting finders, however, have only one brush each (E on S and E on S that travels over the contacts of identifyingwires.

The auxiliary quick-acting finders HS each have an identifying brush or pair of brushes 4 and a group selecting brush 1 which causes the corresponding selectorfinder VS to select the proper calling group. 1 lVhen a subscriber e. g. T removes his receiver from the hook in starting a call an idle quick-acting finder e. g. S rapidly moves its brushes onto the contacts of the calling line. The moment thefinder S starts moving the idle auxiliary quickfinders HS or one of them will be started searching for the wires Z leading to the finder S and will stop when the contacts of these wires are reached. WVe will assume that the connection to the wires P is made The calling subscriber T will then be connected through his line wire A S Z brushes of H8 to the primary link circuit. If the exchange is a semi-automatic one this link circuit will includethe keyboard BS of an operator.

According as the call comes from group I or group II the brushl of the auxiliary quick-finder will stop on a contact segment 2 or 3 and will thus connect the battery to a test relay 79 or 79 If the call comes from group I, as assumed in the present case, the test relay 79 will thus be rendered active and the selector finder VS, which starts moving its brushes as soon as the auxiliary finder stops, will hunt for a free secondary link circuit amongst the link circuits L L L belonging to thefirst group I. If the call had come from the second group II the brush I of the auxiliary quickfinder would have stopped'on the segment 3 and would have rendered the second test relay 7) active. This would have resulted in the selector finder VS confining its testing action to the secondary link circuits L L L of the second group.

When the selector finderVS finds an idle secondary link circuit erg/L 1 the test relay 29 is energized and closes its contacts. It thus connects two. brushes E13 E13 of the identifyingcircuits, to the contacts 5 and 6. According as the call came through the quick-acting finder S or S the brush a of the auxiliary quick-finder HS will be resting on 5 or 6 In the case assumed the brush 4 will be resting'on 6 and therefore battery will be connected from the negative pole through a wire of Z and through 4 6 to the identifying brush E13 only, the other brush E13 being dead. The battery connection to EB extends to, 6Z2 and to the upper winding of the relay R which controls the stopping of the slow-acting finder V that belongs to the secondary link circuit L which was seized bythe selector finder VS Thus only the upper winding of the relay R whose brush e62 travels over the contacts of identifying wires such as 62 leading to the quick-acting finder S is active.

If the call had been extended to HS- through the other quick-acting finder S only the lower winding of R and the corresponding brush 651 that travels over the identifying wires leading to S would have been rendered active, because the brush 4 of HS would then have. stopped on contactb An energizing circuit for B is closed when the brush e52 reaches the contact that is connected to the wire e2 upon which the quick-acting finder S that took the call is resting. It will not be possible for an energizing circuit for R to be closed by the brush e52 on any other wire because the wire c2 can only be connected to the positive pole of the battery by the brush E of S and not by any other quick-acting finder S lVhen the brush 662 of V which is started moving as soon as the secondary link circuit L is seized, reaches the contact of the wire 62, with which the brush E made connection, an energizing circuit including the upper winding of R is closed. This circuit may be traced from the negative pole of the exchange battery through the left wire Z pair of 'brushes 4: 6 E132, e12, upper winding of R upper b-rushebQ, e2. brush E to the positive pole of the battery. The stopping relay R immediately opens its contact 9 and thus opens the circuit of the power device (not shown) that drives the brushes of V During the (time in which the slow-acting finder is travelling towards the contacts of the calling line, the operator may besettin-g up the other .end of 

